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Air Gap and Non-Air Gap R.O. Faucets

What is a Non-Air Gap or Air Gap R.O. Faucet ?

Reverse Omosis (RO) Faucets come in many different styles and finishes. They are also manufactured with either an Air Gap or a Non-Air Gap feature, and some are capable of both. An Air Gap prevents backflow of reject water, back into the R.O. System. This backflow prevention is built into the base of the R.O. Faucet.   The idea is to remove the remote possibility of wastewater, sewage, etc. backing up into the reverse osmosis system and contaminating the potable water supply or RO system components.

When the reject water is coming from the R.O. System and being directed to the drain under the sink, it goes up in to the R.O. Faucet first, then down across the gap of air, into another tube which is then directed into the drain for the kitchen sink. There is a hole drilled in the side of the base of the R.O. Faucet where the air gap is, so IF the reject water were to ever backflow up towards the Faucet, it would simply run out of the drilled hole, into the kitchen sink. The easy way to tell if your faucet is an Air Gap or Non-air Gap, just look for the hole in the side of the base of the faucet. If there is not a hole, you do not have an Air Gap Faucet. This is referred to as a NON-Air Gap R.O. Faucet. Another way to tell, an Air Gap Faucet will have THREE connections on the bottom side of the base of the Faucet.

An Air Gap R.O. Faucet has three water connections :

  1. At the bottom of the threaded stem of the faucet is the main pure water supply connection. The connection can be made with a traditional brass 1/4" compression fitting, or some faucets have a length of 1/4" tubing already affixed to the faucet. In this case, most R.O. Systems have a 3/8" supply, so you would need a 3/8" X 1/4" quick connect reducer to connect the two different sizes.
  2. The second connection of an Air Gap Faucet is the 1/4" reject water line from the R.O. System. This line is always 1/4" from the R.O. and connects to the faucet with a barbed connection. So the 1/4" tubing simply pushes on to the barbed fitting. This reject water is coming from the R.O. under pressure. 
  3. The third connection of an Air Gap Faucet is the 3/8" drain line, coming down from the bottom of the faucet, going to the drain saddle at the sink drain. This is a larger 3/8" tube since the reject water has dropped over the gap of air in the base of the R.O. Faucet, and is no longer under pressure. This connection at the faucet is also made with a barbed fitting.

How do you know if you need an Air Gap R.O. Faucet?

Air gap faucets are required in some areas by local plumbing codes. You will need to check your local plumbing code to see if you are required to install an air gap faucet. In some areas you can install a check valve in the drain line for backflow prevention. Some R.O. Systems have a check valve and flow restrictor combined in one piece. This allows the use of a Non-Air Gap faucet.

Noise from an Air Gap R.O. Faucet can sometimes be an issue. With the Air Gap, water is running thru the base of the faucet, across the gap of air, then down to the sink drain. This function can be a little noisy. Of course with the Non-Air Gap Faucet, the reject water from the R.O. System is going directly from the R.O. to the drain. This is a much quieter operation. Either type of R.O. Faucet will work on any R.O. System.